Multi-speed transmission

ABSTRACT

A planetary transmission includes four planetary gearsets, two of which are simple planetary gearsets and two of which are compound planetary gearsets. A first of the planetary gearsets has members selectively connectible with a ground or stationary member through a synchronizer clutch. A second, third, and fourth of the planetary gearsets have at least one member continuously interconnected with a ground or stationary member. A plurality of synchronizer clutches are employed between the planetary gearsets, which are manipulatable to establish at least seventeen forward speed ratios and one reverse speed ratio between an input shaft and an output shaft of the transmission.

TECHNICAL FIELD

[0001] This invention relates to multi-speed transmissions and, moreparticularly, to multi-speed transmissions having a plurality ofsynchronizer clutches that are manipulated to engage at least seventeenforward speed ratios and at least one reverse speed ratio.

BACKGROUND OF THE INVENTION

[0002] Transmissions utilized with large trucks, such as over-the-roadvehicles, include transmissions having between twelve and sixteenforward speed ratios. In many instances, the transmissions currentlyavailable are actually a pair of separate transmissions arranged inseries to obtain the high number of forward speeds with less pairs ofgears. This concept of two transmissions in series causes the ratioprogression to repeat as the transmission is stepped up or down throughthe speed ratios. This makes a geometric progression of the speed ratiosthe most practical. The vehicles have also generally been designed toexpect a top gear, or maximum forward ratio of 1:1, which requires theaddition of content to the planetary manual design transmissions. Forthis reason, most of the commercial trucks employ countershaft-typetransmissions wherein a plurality of synchronizer or mechanical clutchesare included to establish the required speed ratios.

[0003] As is well known with countershaft-type transmissions, the inputshaft of the transmission generally drives a head gear set which thenprovides input speed to a countershaft on which a plurality of ratiogears are positioned. The ratio gears mesh with gears on thetransmission main shaft, which is generally connected with thetransmissions output shaft. Synchronizers or mechanical clutches on oneof the shafts, main shaft or countershaft, are engaged to establish adrive connection between the respective shaft and gear member therebythe speed ratio on the countershaft to the main shaft is completed.

[0004] Planetary-type manual transmissions generally include a splittergear or splitter planetary set forward of the multi-speed planetary set.For the most part, the planetary set is generally set to provideanywhere from six to eight forward speed ratios and the splitter setdoubles that number of speed ratios. However, it is required that thespeed ratios of the multi-speed planetary gearset be arranged such thatthe splitter gear set can effectively provide intermediate ratios. Forthis reason, the splitter gear set is usually alternately operated in anunderdrive ratio and an overdrive ratio when the multi-speed planetaryportion of the transmission is put through its extended range ofgearing.

SUMMARY OF THE INVENTION

[0005] It is an object of the present invention to provide an improvedmulti-speed planetary transmission employing synchronizer clutches toprovide the desired interconnections between the planetary gearsets ofthe planetary transmission.

[0006] In one aspect of the present invention, four planetary gearsetsare arranged in series power flow construction.

[0007] In another aspect of the present invention, at least three of theplanetary gearsets have an input synchronizer and an outputsynchronizer.

[0008] In yet another aspect of the present invention, each of thesynchronizer clutches is operable to provide two ratios within each ofthe planetary gearsets.

[0009] In still another aspect of the present invention, the threeplanetary gearsets all have one member connected continuously to aground member such as a transmission housing.

[0010] In a further aspect of the present invention, one of theplanetary gearsets has a synchronizer clutch connecting at least twoplanetary members of the transmission housing and the input synchronizerof a downstream planetary gearset provides output drive from this oneplanetary gearset.

[0011] In yet still another aspect of the present invention, an inputclutch is provided to disconnect the planetary gearset from the drivingengine when it is desired to provide a ratio interchange in theplanetary transmission.

[0012] In a yet still further aspect of the present invention, two ofthe planetary gearsets are simple planetary gearsets and two of theplanetary gearsets are compound planetary gearsets.

[0013] In another aspect of the present invention, the first of theplanetary gearsets is operable through the judicious selection of thegrounding synchronizer to provide a reverse speed ratio and a forwardunderdrive ratio.

[0014] In yet another aspect of the present invention, the first of theplanetary gearsets is operable when the grounding synchronizer is inneutral to provide a direct drive or 1:1 output during portions of theratios of the planetary transmission.

[0015] In yet still another aspect of present invention, two of theplanetary gearsets provide an underdrive ratio, an overdrive ratio, anda direct through-drive condition.

[0016] In a yet still a further aspect of the present invention, whenthe two planetary gearsets providing a direct through-ratio, one of thegear members of each of the planetary gearsets is connected to both theinput and output synchronizer clutch.

[0017] In a yet still further aspect of the present invention, thefourth of the planetary gearsets is operable to provide an underdriveratio and a through drive ratio.

DESCRIPTION OF THE DRAWING

[0018] The drawing is a schematic representation of a powertrainincluding a multi-speed planetary transmission incorporating the presentinvention.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

[0019] Referring to the drawing, there is seen a powertrain, generallydesignated 10, including an engine 12, a planetary transmission 14, anda final drive mechanism 16. The engine 12 is a conventional internalcombustion-type power plant and the final drive mechanism 16 is aconventional differential mechanism, which is adapted to drive thetraction wheels of a vehicle. The planetary transmission 14 includesfour planetary gearsets 18, 20, 22, and 24, seven synchronizer clutches26, 28, 30, 32, 34, 36, 38, and a selectively engageable input clutch40. The input clutch 40 is a conventional mechanical or hydraulicallyoperated clutch, which is engaged and disengaged usually by the operatorto connect and disconnect the engine from the planetary transmission 14.

[0020] The synchronizer clutches 26, 28, 30, 32, 34, and 38 areconventional two-way synchronizers, which have two operating positionsand a neutral condition. The synchronizer clutch 36 is a conventionalthree-way synchronizer mechanism, which selectively permits theconnection of one gear member to an output or two gear members to anoutput. The synchronizer clutch 38 is connected continuously with atransmission housing or ground member 42, which a stationary portion ofthe transmission. Thus, the synchronizer clutch 38 will connect gearmembers with the transmission housing.

[0021] The planetary gearset 18 includes a sun gear member 44, a ringgear member 46, and a planet carrier assembly member 48. The planetcarrier assembly member 48 includes a plurality of pinion gears 50rotatably disposed on a planet carrier member 52 and meshing with boththe sun gear member 44 and the ring gear member 46. The planetarygearset 18 is what is commonly termed a simple planetary gearset; thatis, a single pinion meshes between the sun gear member and the ring gearmember.

[0022] The planetary gearset 20 includes a sun gear member 54, a ringgear member 56, and a planet carrier assembly member 58. The planetcarrier assembly member 58 includes a plurality of meshing pinion gearmembers 59 and 60 that are rotatably mounted on a planet carrier member62 and disposed in meshing relationship with the sun gear member 54 andthe ring gear member 56, respectively. The planetary gearset 20 iscommonly termed a compound planetary gearset. In a compound planetarygearset employing an even number of pinion gears, the ring gear memberand sun gear member rotate in the same direction when the planet carriermember is held stationary.

[0023] The planetary gearset 22 is also a compound planetary gearsethaving a sun gear member 64, a ring gear member 66, and a planet carrierassembly member 68. The planet carrier assembly member 68 has meshingpinions 69 and 70 that are rotatably mounted on a planet carrier member72 and disposed in meshing relationship with the sun gear member 64 andring gear member 66, respectively.

[0024] The planetary gearset 24 includes a sun gear member 74, a ringgear member 76, and a planet carrier assembly member 78. The planetcarrier assembly member 78 includes a plurality of pinion gears 80 thatare rotatably mounted on a planet carrier member 82 and disposed inmeshing relationship with both the sun gear member 74 and the ring gearmember 76. The planetary gearset 24 is a simple planetary gearset.

[0025] The planet carrier member 62 of the planetary gearset 20 isconnected with the transmission housing 42, the sun gear member 64 ofthe planetary gearset 22 is connected with the transmission housing 42,and the sun gear member 74 of the planetary gearset 24 is continuouslyconnected with the transmission housing 42.

[0026] The ring gear member 46 and planet carrier member 52 areconnected with one side of the synchronizer clutch 38 such that eitherof these members may be individually connected with the transmissionhousing 42 and therefore held stationary. The synchronizer clutch 38 hasa neutral condition during which both the sun gear member 44 and thering gear member 46 are free to rotate. The ring gear member 46 andplanet carrier member 52 are also drivingly connected with one side ofthe synchronizer clutch 36, which has an output hub 84 connected to thesun gear member 54 to thereby provide an input member to the sun gearmember 54. Thus, the synchronizer clutch 36 is an input clutch for theplanetary gearset 20.

[0027] The synchronizer clutch 34 is selectively engageable to connectthe ring gear member 56 to an output hub 86 or connect the sun gearmember 54 to the output 86. The output 86 is connected to an input sideof the synchronizer clutch 30. The synchronizer clutch 30 is selectivelyconnectible to the ring gear member 66 and to the planet carrier member72. Thus, the synchronizer clutch 30 will provide a drive connectionbetween the planetary gearset 20 and the planetary gearset 22.

[0028] The synchronizer clutch 32 provides an output clutch for theplanetary gearset 22 that is selectively connectible between the ringgear member 66 and an output hub 88 or connectible between the planetcarrier member 72 and the output hub 88. The output hub 88 is drivinglyconnected with the synchronizer clutch 26. Therefore, the synchronizerclutch 32 connects the output power from the planetary gearset 22 withthe synchronizer clutch 26, which is an input clutch for the planetarygearset 24.

[0029] The synchronizer clutch 26 is selectively engageable to connectthe ring gear member 76 with the output hub 88 or to selectively connectthe planet carrier member 82 with the output hub 88. The synchronizerclutch 28, which provides output drive from the planetary gearset 24, isconnectible with a transmission output shaft 90, which is continuouslyconnected with the final drive mechanism 16. The synchronizer clutch 28is selectively engageable to connect the ring gear member 76 with theoutput shaft 90 or selectively connects the planet carrier member 82with the output shaft 90.

[0030] When the synchronizer clutch 38 is connected between the ringgear member 46 and the ground 42, the planetary gearset 18 will providean underdrive ratio between the sun gear member 44 and the planetcarrier member 52. When the synchronizer clutch 38 is connected betweenthe transmission housing 42 and the planet carrier member 52, theplanetary gearset 18 will provide a reverse speed ratio between the sungear member 44 and the ring gear member 46. When the synchronizer clutch38 is selectively placed in a neutral condition, the ring gear member 46and planet carrier member 52 are free to rotate and the synchronizerclutch 36 can be adjusted or shifted to connect the ring gear member 46and planet carrier member 52 together, thereby providing a direct drivethrough the planetary gearset 18.

[0031] The synchronizer clutch 36 is also operable to connect to eitherthe ring gear member 46 or the planet carrier member 52 individually.Thus, the hub 84 can be driven forwardly at an underdrive ratio,reversely at an underdrive ratio, or at a 1:1 drive ratio therebyproviding these three input ratios through the sun gear member 54 of theplanetary gearset 20.

[0032] The synchronizer clutch 34 can be selectively connected betweenthe ring gear member 56 and the hub 86 such that an underdrive ratio isprovided in the planetary gearset 20 between the sun gear member 54 andthe ring gear member 56. The synchronizer clutch 34 can be selectivelypositioned to engage the sun gear member 54 thereby providing a directdrive through the planetary gearset 20 to the hub 86.

[0033] The synchronizer clutch 30 can selectively engage either the ringgear member 66 or the planet carrier member 72 to thereby connect thesemembers individually with the hub 86. If the ring gear member 66 isconnected with the hub 86 and the planet carrier member 72 is connectedwith the hub 88 through the synchronizer clutch 32, an underdrive ratiois provided at the planetary gearset 22. If the synchronizer clutch 30is selectively engaged with the planet carrier member 72 and the ringgear member 66 is selectively connected with the hub 88 through thesynchronizer clutch 32, an overdrive ratio is provided through theplanetary gearset 22. If the ring gear member 66 is connected with bothsynchronizer clutches 30 and 32, a through-drive or 1:1 ratio isprovided.

[0034] The hub 88, as previously mentioned, provides input drive to thesynchronizer clutch 26. The synchronizer clutch 26, if when connectedbetween the hub 88 and the ring gear member 76, will provide input driveto the ring gear member 76. If the synchronizer clutch 28 is connectedbetween the planet carrier member 82 and the output shaft 90, anunderdrive ratio will be provided in the planetary gearset 24. If thesynchronizer clutch 26 is selectively engaged with the planet carriermember 82 and the synchronizer clutch 28 is selectively engaged betweenthe ring gear member 76 and output shaft 90, an overdrive ratio isprovided in the planetary gearset 24. If both synchronizer clutches 26and 28 are connected with the ring gear member 76, a direct drive isprovided through the planetary gearset 24.

[0035] The following two tables provide the engagement sequence andpossible speed ratios for the planetary transmission 14. In thefollowing tables, C1 equals planet carrier member 82, C2 equals planetcarrier member 72, C3 equals planet carrier member 62, C4 equals planetcarrier member 52; S1 equals sun gear member 74, S2 equals sun gearmember 64, S3 equals sun gear member 54, S4 equals sun gear member 44;R1 equals ring gear member 76, R2 equals ring gear member 66, R3 equalsring gear member 56, and R4 equals ring gear member 46.

[0036] The number of teeth on ring gear member 76 equals eighty-nine,the number of teeth on ring gear member 66 equals eighty-nine, thenumber of teeth on ring gear member 56 equals eighty-seven, and thenumber of teeth on ring gear member 46 equals ninety. The number ofteeth on sun gear member 74 equals thirty-five, the number of teeth onsun gear member 64 equals thirty-five, the number of teeth on sun gearmember 54 equals forty-five, and the number of teeth on sun gear member44 equals twenty-six.

[0037] The ring gear/sun gear tooth ratio for the planetary gearset 24is 2.543. The ring gear/sun gear tooth ratio for the planetary gearset22 is 2.543. The ring gear/sun gear tooth ratio for the planetarygearset 20 is 1.923. The ring gear/sun gear tooth ratio for theplanetary gearset 18 is 3.462. These numbers are utilized to calculatethe speed ratios for the planetary gearsets 24, 22, 20, and 18 as shownin the table below.

[0038] Following the engagement schedule of the truth table below, thoseskilled in the art will readily recognize the power flow paths that areavailable through the planetary transmission 14. By way of example, inthe reverse high ratio, power flows from the engine through the clutch40 to the sun gear member 44 and through the planetary gearset 18 to thering gear member 46 and the hub 84. The power flow at the hub 84 flowsto the sun gear member 54 and through the planetary gearset 20 to thering gear member 56, which provides power flow to the planet carriermember 72 and through the planetary gearset 22 to the ring gear member66, which delivers power flow to the planet carrier member 82, whichdelivers power through the planetary gearset 24 to the ring gear member76, which is connected with the output shaft 90.

[0039] Thus, in reviewing the chart below, the planetary gearset 18 isin a negative underdrive condition, the planetary gearset 20 is in apositive underdrive condition, the planetary gearset 22 is in a positiveunderdrive condition, and the planetary gearset 24 is in a positiveunderdrive condition. This gives a total reverse low ratio of −15.368.It will be noted in the seventeenth forward speed ratio that all of theplanetary gearsets are passing direct drives and the overall speed ratioof the planetary transmission is one. It will also be noted that thestep ratio between adjacent forward speed ratios is identical for ratiosone through sixteen, and the ratio between the sixteenth forward speedratio and the seventeenth forward speed ratio is 1.17 which is slightlyless than the 1.18 step ratio between the other forward speed ratios.

[0040] The ring gear/sun gear tooth ratios can, of course, be varied,which will change the speed ratios for each of the planetary gearsets.Therefore, the ring gear/sun gear tooth ratios given above are forexample purposes only and are not intended to be limiting features ofthe present invention. The ring gear/sun gear tooth ratios given wereselected to provide a constant step ratio between forward speed ratios.In the following table, when a synchronizer is designated “Open” it isin a neutral condition (i.e. not transmitting power). TABLE 1 CombinedPlanetary Planetary Planetary Planetary Gear Tq Ratio Step (24) (22)(20) (18) Rev −7.917 0.718 1.648 1.933 −3.462 Hi Rev −11.030 1.000 1.6481.933 −3.462 Med Rev −15.368 1.393 1.648 1.933 −3.462 Lo −1.08 1 14.2161.000 1.648 1.933 4.462 1.18 2 12.018 1.393 1.000 1.933 4.462 1.18 310.204 0.718 1.648 1.933 4.462 1.18 4 8.626 1.000 1.000 1.933 4.462 1.185 7.292 1.393 0.607 1.933 4.462 1.18 6 6.191 0.718 1.000 1.933 4.4621.18 7 5.234 1.000 0.607 1.933 4.462 1.18 8 4.440 1.393 1.648 1.9331.000 1.18 9 3.756 0.718 0.607 1.933 4.462 1.18 10 3.186 1.000 1.6481.933 1.000 1.18 11 2.694 1.393 1.000 1.933 1.000 1.18 12 2.287 0.7181.648 1.933 1.000 1.18 13 1.933 1.000 1.000 1.933 1.000 1.18 14 1.6341.393 0.607 1.933 1.000 1.18 15 1.388 0.718 1.000 1.933 1.000 1.18 161.173 1.000 0.607 1.933 1.000 1.17 17 1.000 1.000 1.000 1.000 1.000

[0041] TABLE 2 Synchro Synchro Synchro Synchro Synchro Synchro SynchroGear 26 28 30 32 34 36 38 Rev C1 R1 C2 R2 R3 R4 C4 Hi Rev R1 R1 C2 R2 R3R4 C4 Med Rev R1 C1 C2 R2 R3 R4 C4 Lo 1 R1 R1 C2 R2 R3 C4 R4 2 R1 C1 R2R2 R3 C4 R4 3 C1 R1 C2 R2 R3 C4 R4 4 R1 R1 R2 R2 R3 C4 R4 5 R1 C1 R2 C2R3 C4 R4 6 C1 R1 R2 R2 R3 C4 R4 7 R1 R1 R2 C2 R3 C4 R4 8 R1 C1 C2 R2 R3R4 & Open C4 9 C1 R1 R2 C2 R3 C4 R4 10 R1 R1 C2 R2 R3 R4 & Open C4 11 R1C1 R2 R2 R3 R4 & Open C4 12 C1 R1 C2 R2 R3 R4 & Open C4 13 R1 R1 R2 R2R3 R4 & Open C4 14 R1 C1 R2 C2 R3 R4 & Open C4 15 C1 R1 R2 R2 R3 R4 &Open C4 16 R1 R1 R2 C2 R3 R4 & Open C4 17 R1 R1 R2 R2 S3 R4 & Open C4

[0042] During the first-to-second forward speed ratio interchange, thesynchronizer clutches 28 and 30 are manipulated. During thesecond-to-third forward speed interchange, the synchronizer clutches 26,28, and 30 are manipulated. During the third-to-fourth forward speedinterchange, the synchronizer clutches 26 and 30 are manipulated. Duringthe fourth-to-fifth forward speed interchange, the synchronizer clutches28 and 32 are manipulated. During the fifth-to-sixth forward speedinterchange, the synchronizer clutches 26, 28, and 32 are manipulated.During the sixth-to-seventh forward speed interchange, the synchronizerclutches 26 and 32 are manipulated. During the seventh-to-eighth forwardspeed interchange, the synchronizer clutches 28, 30, 32, 36, and 38 aremanipulated. During the eighth-to-ninth forward speed interchange, thesynchronizer clutches 26, 28, 30, 32, 36, and 38 are manipulated. Duringthe ninth-to-tenth forward interchange, the synchronizer clutches 26,30, 32, 36, and 38 are manipulated. During the tenth-to-eleventh forwardspeed interchange, the synchronizer clutches 28 and 30 are manipulated.During the eleventh-to-twelfth forward speed interchange, thesynchronizer clutches 26, 28, and 30 are manipulated. During thetwelfth-to-thirteenth forward speed interchange, the synchronizerclutches 26 and 30 are manipulated. During the thirteenth-to-fourteenthforward speed interchange, the synchronizer clutches 28 and 32 aremanipulated. During the fourteenth-to-fifteenth forward speedinterchange, the synchronizer clutches 26, 28, and 32 are manipulated.During the fifteenth-to-sixteenth forward speed interchange, thesynchronizer clutches 26 and 32 are manipulated. During thesixteenth-to-seventeenth forward speed interchange, the synchronizerclutches 32 and 34 are manipulated.

[0043] Note that the planetary gearset 20 remains in the underdrivecondition for all drive conditions except the seventeenth speed ratio.It should also be noted that the seventeenth forward speed ratio hasbeen limited to 1:1. Those skilled in the art, however, will recognizethat there are at least three overdrive ratios, which are not includedin the truth tables.

1. A multi-speed power transmission comprising: an input shaft; anoutput shaft; a stationary housing member; a first planetary gearsethaving a sun gear member continuously connected with said input shaft, aring gear member, and a planet carrier member; a second planetarygearset having a sun gear member, a ring gear member, and a planetcarrier member; a third planetary gearset having a sun gear member, aring gear member, and a planet carrier member; a fourth planetarygearset having a sun gear member, a ring gear member, and a planetcarrier member; a first synchronizer clutch having two active positionsfor selectively individually interconnecting said ring gear member andsaid planet carrier member of said first planetary gearset with saidstationary housing and a neutral position; a second synchronizer clutchhaving three active positions to selectively interconnect said ring gearmember, said planet carrier member, and both said ring gear member andsaid sun gear member of said first planetary gearset with said sun gearmember of said second planetary gearset; a third synchronizer clutchhaving two active positions for selectively interconnecting said ringgear member and said sun gear member of said second planetary gearsetwith a fourth synchronizer clutch; said fourth synchronizer clutch beingselectively operable in two active positions to interconnect said thirdsynchronizer clutch individually selectively with said ring gear memberand said planet carrier member of said third planetary gearset; a fifthsynchronizer clutch having two active positions for selectivelyinterconnecting individually with said ring gear member and said planetcarrier member of said third planetary gearset with a sixth synchronizerclutch; said sixth synchronizer clutch being selectively operable in twoactive positions to individually interconnect said fifth synchronizerclutch with said ring gear member and said planet carrier member of saidfourth planetary gearset; a seventh synchronizer clutch having twoactive positions and being selectively engageable therein toindividually interconnect said ring gear member and said planet carriermember of said fourth planetary gearset with said output shaft; said sungear members of said third and said fourth planetary gearsets beingcontinuously interconnected with said stationary housing; said planetcarrier member of said second planetary gearset being continuouslyinterconnected with said transmission housing; and said synchronizerclutches being selectively engageable in a plurality of combinations toestablish at least seventeen forward speed ratios and a reverse speedratio between said input shaft and said output shaft through saidplanetary gearset.
 2. The multi-speed power transmission defined inclaim 1 further comprising: an input clutch selectively connectiblebetween a prime mover and said input shaft.
 3. The multi-speed powertransmission defined in claim 2 further wherein: each of saidsynchronizer clutches is selectively active in at least one of theirrespective active positions to establish eight of said forward speedsand said one reverse speed.
 4. The multi-speed power transmissiondefined in claim 2 further wherein: each of said synchronizer clutchesis selectively active in at least one of their respective activepositions to establish eight of said forward speeds and said one reversespeed; and said first synchronizer clutch is in said neutral position,said second synchronizer clutch interconnects both of said ring gearmember and said planet carrier member of said first planetary gearsetwith said sun gear member of said second planetary gearset, and saidthird, fourth, fifth, sixth, and seventh synchronizer clutches areselectively active in at least one of their active positions during nineof said forward speed ratios.
 5. The multi-speed power transmissiondefined in claim 4 further wherein: said third synchronizer clutch is inthe same active position during sixteen of said forward speed ratios andsaid reverse ratio.
 6. The multi-speed power transmission defined inclaim 2 further wherein: at least three reverse speed ratios areestablishable through said planetary gearsets and each of saidsynchronizer clutches is selectively active in at least one of theactive positions during each of the three reverse speed ratios.